Radio system



Jan. 6, 1925 1.5213777 D. G. MQCAA RADIO SYSTEM Filed July 18; 1923 3Sheet-Sheet 2 1 ATTORNEY.

-j, 6,1925. v I 3,521,???

. M 'D.G.MCCAA RADIO SYSTEM I Filed July 18. 1923 3 sheets -shet- 5 l NVEN TOR.

m d M BY M43455 1 ATTORNEY.

Patented Jan. 6, was. A

DAVID G. MCCAA, LANCASTER, PENNSYLVANIA, ASSIGNOR TO THE ELECTRICAPPARATUS co.,-oF PARKESBURG, PENNSYLVANIA, A coRPoaA'rIoN or RADIOSYSTEM.

SYLVANIA.

Application filed July 18, 1923. Serial No. 652,2 19.

To all whom it may concern:

Be it known that I, DAVID G. M CAA, a citizen of the United States,residing in Lancaster, county of Lancaster, 'State of Pennsylvania, haveinvented new and useful Improvements in Radio Systems, of which thefollowing is a specification.

y invention relates to thereception of high or radio frequency energy,without in terference or disturbance due to other high.

or radio frequency energy produced artificially or by naturalelectricity, as static, atmospherics, etc., in. systems in which theenergy is transmitted either through the 1 natural media or over aconductor or condu-ctors extending between transmitting and receivingstations, for-purposes of effecting at receiving stations controls, orsignals which may be either telegraphic -or telephonic. v

i In accordance with my invention, the frequency of the energy whichit,is desired should be excluded or reduced in" effect and representedby oscillations set up by static, 2 atmospherics or other naturalelectricity, is caused to differ from the frequency of the energy whichit is desired shall be received, "and the the undesired oscillations areneutralized by an opposing and substantially equal potential caused bythe received undesired oscillations, leaving the desired oscillations toeffect the desired signals or controls with no or substantially nodisturbance by the undesired oscillations; andpreferably the undesiredoscillations due to static or at ier natural electricity are caused tohave but a single frequency. And'when the undesired high or: radiofrequency oscilla- 'tions are artificially produced, as by trans-f 40mitters' emitting oscillations of frequency difl'e'ring from the desiredoscillations, their disturbing effects are-similarly eliminated orreduced. 1

Further in' accordance with my invention,

' the desired oscillations,preferably first amplificd, are utilized tochange the reactance of a circuit or path in which both the desired andundesired signals are received to materially increase the ratio of theamplitude of the desired oscillations to the amplitude of the undesiredoscillations. Similarly, with regard to undesired oscillationsartificially produced and having a frequency different from-the desiredoscillations, the desired oscillations, preferably firstamplified,effect a change of reactance of a circuit, in which both the desired andundesired oscillations arev received to render the aircuit or pathresonantto the desired oscillations and de-tuned or non-resonant withrespect to the undesired oscillations. I

Further in accordance with my invention, a. local source of high orradio frequency oscillations, having a frequency differing from thedesired oscillations, is utilized to;

reactance whereby the effect a variation of desired oscillations arecaused to partake of maximum amplitude/in a certain part. or branch ofsaid'cireuit or path and thereb increase the ratio of the effect of thedesired oscillations to the efl'ect of the undesired oscillations in theultimate translating instrument.

device or signal-translating And in case the desired energy is that ofundamped waves, the oscillations produced by the local source serve inaddition to effect, for telegraphy,

oscillations and the thereby producegan audible signal. My inventionresides in the method and PENN- periodic variation in I the combinedeffects of the locally produced desired oscillations to apparatus of thecharacterhereinaften described. For an. understanding; of my method, andfor.an"illustration of some of the various forms my apparatus may take,reference is to be had to the accompanying drawings, in; which: I -Fig.1 is a' diagrammatic view of radio receiving apparatus embodying myinvention.

Figs. 1 and 1 are diagrammatic views'of modifications of the. systemshown in Fig. 1.

Fig. 2 is a diagrammatic view of appa rat-us in accordance with myinvention in which the absorption structure is in the form of a loopaerial or antenna and in which the desiredoscillations operate moredirectly upon the receiving circuit or path.

Figsr3, 4 and 5 are diagrammatic views of further modifications.

Fig. 6 is a diagrammatic view of further modifications of my inventionrelating in. part to telegraphy. i

Referring to Fig. 1, A represents generically any absorption structureof a radio inventionwill be described in connection with radio receivingsystems utilized either for effecting. a control or controls of anycharacter, as for controlling movements of ships or aircraft, picture ormotion picture apparatus, or signaling apparatus in general, includingtelegraphic and telephonic apparatus, it being understood that thetranslating instrument T hereinafter referred to may be asignal-translating instrucomprising anode p,

lating instrument T, as a telephone,

'quency amplifier,

,ment, as a telephone, or any other translating instrument for effectingany suitable control In the path between the anterma A and earth orcounter-capacity E are included the variable tuning condenser C, whichmay be omitted if suitable or desirable, the primary P of an oscillationtransformer preferably variably coupled to its secondary S, and theinductance L. 1 In circuit with the secondary S are'the variable tuninginductance L? and condenser Cf, switch 8 and variable inductance L inshunt toWhich latter are-seriall connected the variable tuning condenser(i and variable tuning inductance L to whose termina ls is connectedthe'grid circuit of a de tector of any suitable character, preferably athermionic'detector Vtof the audion type 'gridg and filament or cathodef In the connection to the grid is included the fixed condenser Cshunted by a grid leak resistance 1', as commonly em ployed inconnection with audion detector tubes. In the anode or plate circuit isthe source of current or battery 13 and the transand the driver coil orwinding of an oscillation transformer whose secondary F is connectedthrough the switch sZ in parallel with the inductance L. Inasmuch as thedetector tube V as employed in this example of my invention is utilizedalso as a radio frethe battery B and transformer Tare preferablyshuntedby a radio frequency by-pass condenser C The circuits S, L C IFand L C Ii have a common connection a to earth or counter-capacity E. Xin the absorption circuit or antenna path A represents a point of rel:atively high potential, and preferably coincides approximately with apoint ofpotential anti-node. That is to say, X is preferably a point inthe electrical length ofthe antenna path above capacity E at whichexists a high potential or anti-node of potential. The point X ,is

the earth or counterconnected through the preferably variable condenserC with a point Y common to the two circuits S, L C L andL C L The modeof operation is as follows: Assuming first that the windings D and F areomitted, or are not functioning, as when the switch 8 is open, isattuned, when: the switch s is open, to the frequency of theoscillations representing the desired signal or control by suitablyadjusting C, P, L, or any two or more of them; and the circuit L C L issimilarly attuned to the frequency of the oscillations of the desiredsignal or control, as by. adjusting L (J or L or any two or more ofthem; Thereafter, the antenna path is de-tuned with respect to thefrequency of the desired oscillations, as by adjusting C, I L, or anytwo or more of them. Thereupon, the-switch s is closed, and the circuitS, L G L is .attuned to the now period of the antenna path by varying Lor C or both, leaving L as previously adjusted when tuning the circuit LC L to the frequency of the desired oscillations. L Assuming that duringthe reception of :signals there exists a natural atmosphericdisturbance, as static, strays atmospherics, etc., there will be set upin the antenna path oscillations of a frequency determined by thenatural period of the antenna path, and that, frequency -w111 be eitherhigher or lower than the frequency of the oscillations representing thedesired signal or control; Energy represented by the oscillations offrequency difierent from the signal frequency will be transferredthrough the coupling PS into the circuit of the secondary S, which hasbeen attuned to the frequency of the undesired oscillations, and therethen exists across the terminals of the inductance L anelectro-motive-force dependent upon the amplitude of the undesiredoscillations in the circuit of the secondary S, and suchelectro-motive-force affects the grid circuit of the tube V, andtherefore the translating instrument T. But by connecting the points Xand X directly, as when condenser C isomitted, these points are closelycoupled, and there is impressed across the terminals of the inductance Lan electro-motive-force of such magnitude and in such phase relationwith respect .to the undesired oscillations in the circuit of thesecondary S that the electro-motiveforce so impressed by the couplingmore or less completely opposes the electro-inotiveforce across theterminals of the inductance L due to the oscillations in the circuit ofthe secondary S, with the result that the effect of the undersiredoscillations upon the grid circuit of the tube V, and therefore upon theinstrument T, isreduced. However, it is desirable that the couplingbetween the points X and Y be a more or the antenna path across theterminals of the inductance L force impressed by the coupling,

due to the oscillations of undesired frequency in the circuit of thesecondary S. The result is that there is not impressed upon the circuitL G I not upon the grid circuitof the tube V, any

effect due to the oscillations of undesired frequency which, as stated,are due to static or other natural atmospheric disturbances, and theresult is that the signal-translating finstrument T is practicallycompletely shielded from the effects of undesired oscillations. For theurpose described it is desirable that the eliactro-motive-fore impressedacross the terminals of the inductance L through the coupling C shall bein opposite phase to and substantially equal in amplitude to theelectro-motive-force existing across the terminals of the inductance Ldue to the oscillations of undesired frequency in the circuit of thesecondary S. The adjustment of the condenser C5 controls the amplitudeof the electro-motivewhile variation of the'coupling between the primaryP and secondary S determines the amplitude of the electro-motive-forceacross the terminals of the inductance L due to A the oscillations inthe circuit of the secondary S. Therefore, by suitably varying the 0condenser C coupling of PS and the capacity of the or both, the deslredoptimum adjustment for the purposes described is effected. Furthermore,as regards phase relations, the sense of coupling as between P and S isof importance, and this sense of coupling is readily reversible toprocure the end sought either by reversing the sense of connection ofeither P or Sin its circuit, or when the coils rotatable with respect toeach other one of them may be rotated to such position that the sense ofcoupling is reversed and made suitable for the purposes described. Theelectro-motive-force at the point X isninety degrees out of phase withthe current in the antenna'path; and the eleetro-motive-force ln'thecircuit of the secondary S is to similar extent out of phase with thecurrent in the circuit of the primary P, and accordingly, by properlychoosing the sense of coupling between P and S the aforesaid phaserelations suitable for readily obtainable.

With the effect of the undesired oscilla tions upon the detector V andinstrument T reduced or eliminated as described, a very C and thereforeP and S are relatively.

the result described are I large proportion of the energy of theoscillations of the desired signal or controlexist ing in the antennapath, and of frequency different from the frequency of the oscillationsin the circuit of the secondary S, passes by way of the coupling X, C,Y, inductance L and connection a to the earth or countercapacity E,setting up an electro-motivef disturbance by the. undesiredoscillations.

Inasmuch as the circuit of the secondary S is de-tuned with respect tothe frequency of the desired signal or. control oscillations,

"there is practically no energy representing the desired. signalor ofthe secondary It will be understood concerning the forecontrol in thecircuit desired siggoing description of operation that the deslredsignals or controls may be represented either by trains of decadentwaves, such as emitted by a spark transmitter, or may be non-decadent orsustained or undainpe'd waves, as in telephony. j Assuming that when theenergy of the desired signal or control is being received there exist inthe natural media or are otherwise impressed, upon the path of theantenna oscillations of frequency differing from the frequency of theoscillations representing the desired signal or control, the sameresults are attained, but in such event the antenna path and the circuitof the secondary S are attuned to the frequency of the undesiredoscillations.

While in the operation above :described the antenna circuit or path isde-tun'ed as regards the desired signal or control waves, it may be leftattuned to the frequency of the desired signal or control waves, and thecircuit ofthe secondary S is then attuned to a frequency different from'the frequency of the waves of the desired signal or control, andtherefore different also from the now equal frequency of the'waves dueto static or other atmospheric disturbance. In

llli

this event, the advantages of myinvention the like are'often orgenerally in the form of highly decadent waves, and therefore a largeproportion of the'energy of the decadent waves will nevertheless appearin the circuit of the secondary .S, and their effect, as upon the gridcircuit of the tube V, is reduced or eliminated by the coupling effectedbetweenthe points X and Y. The circuit of the secondary S being de-tunedwith respect "to the the circuit of the secondary &

if at all, affected by and therefore,

absorb practically no signal or control energy, but absorbs a relativelylarge proportion of the energy due to static or the like v. andrepresented by the decadent waves.

\The arrangement first above described is byxitself of great advantage,notwithstanding thefact that the antenna path is detuned with respect tothe frequency of the desired signal or control waves, with the resultthat the oscillations representing the desired signal or control are oflesser amplitude than if the antenna path were attuned to theirfrequency.

The aforesaid disadvantage may be largely or wholly overcome, however,by recourse to the windings D and F. With the switches s and '8 open,the antenna path is attuned to the frequency of the desired signal orcontrol oscillations, and the circuit L C L is attuned to the samefrequency. The switch 8 is then closed,

thereby bringing the winding F into parallel with the winding L, theinductance of the winding F preferably being considerably smaller thanthe inductance of L. With the inductance of F in parallel to theinductance L, the antenna path is now detuned to the signal frequency,and the frequency of the oscillations due to static or the like ishigherthan the signal frequency' At the point X, then, there existelectro-motiveforces of signal frequency and of a higher frequency, andby virtue of the coupling from X to Y these ,electro-motive-forces areimpressed across the terminals of the inductance L, theelectro-motiVe-force of signal frequency relatively greatly alfectiiggthe potential of the grid 9 of the .tube while the electro-motive forceof higher frequency due to static influences the grid 9 to far lesserdegree; The signal-representing oscillations are not only detected bythe tube V,.but are also amplified, and there accordingly traverses thewinding D acurrent having radio frequency equal to the signal frequencyWith proper sense of coupling between D and F, D will cause by inductionacross the terminals of the inductance F an elcetro-motivc-force of suchmagnitude, as may be determined by the degree of coupling, and in suchdirection, due to the sense of coupling, that current of signalfrequency will be excluded from the winding F, the effect being the sameas if the inductance of the'coil F were. greatly increased, and thedegree of change of the inductance of the winding F as influenced by thecurrent in the winding D may be or preferably is made such that Whilecurrent of signal frequency is traversing the signal or control will' Soperates to from the period of the signal fre uency upon the grid 9 isenhanced, with correspondingly greater respouse by or in the telephoneBy use of the arrangement such as D, F, the period of the antenna pathdiffering signal oscillations is caused to become equal to the period ofthe signal oscillations. It will be understood, however, that, ingeneral, by reversing the sense of coupling'between D and F, the reverseefiect may be obtained, that isto say, the inductance of F may bedecreased, and correspondingly changing the natural period of theantenna path.

' 1n the last above description, the circuit of the secondary S has notbeen utilized, and some of the energy of oscillations due to staticfinds its'way into the circuit L C L and may have some effect upon theinstrument T. But this effect may beredu'ced or eliminated by closingthe switch 8 and tuning the circuit of the secondary S to the aforesaidhigher frequency of the oscillations due to static, whereupon thepotential difference between the terminals of the inductance L due tothe frequency of the undesired oscillations is counteracted by thesubstantially equal and opposite potential impressed thereon by thecoupling X, Y, and accordingly there is substantially no effect upon thegrid g, and therefore upon the instrument T, due to static.

these circumstances, the current in the coil Dis entirely that due to orrepresenting the signal, and, as aforesaid, no current of signalfrequency is admitted to the coil F, and the period of the antenna pathis restored to equality or substantial equality with the frequency ofthe signal, as above described. Under these circumstances, a greaterportion of the static in the antenna path passes to the earth orcounter-capacity E throu *mitted to flow through coil F by the currentof signal frequency traversing the coil D.

Such feeble energy of oscillations due to static as may be transferredfrom coil F 'tocoil D,.and thence through the capacity existing betweenthe anode p and grid 9 is counteracted by the potential existing acrossthe terminals of the inductance L as imposed thereon by the coupling X,Y and the circuit of the secondary S.

The operation involving the use of the coil D or coil F and circuit ofthe secondary S above described is the same when the disturbing effectis that of undamped or damped waves impressed upon the antennapathandhaving a frequency differingfrom the signal frequency.

The arrangement of Fig. 1 is in, general the same as that of Fig. 1.However,

Under ployed a. variable cougling capacity C,.

whereby the-circuits L ,C C, and

C C, L are,electro-statically coupled.

In F l thearrangement is in general similar to that of Fig. 1, exceptthat the condenser C of F ig. 1 is omitted, with the result that thecoupling between the circuits S, L, C and C C L is closer or tighterthan in the arrangement of Fig. 1*.

It will be understood that in the arrangements above described there mayprecede the detector V one or more stages of radio frequency amplifiers,and that the winding D, may be in the anode circuit of any one of themor may remain in the anode circuit of the tube V. It will further beunderstood that in place of the translating instruments T there may beinserted the primary of an audio frequency transformer whose secondarycontrols the potential of the grid of an audio frequency amplifier, thenumber of stages of' audio frequency amplification being multiplied, ifdesired, and the signal or control instrument T will be connected in theanode Circuit of the last stage.

' Referring. to Fig. 2, in lieu of an open or ordinary aerial or antennathe absorption. structure comprises the stationary or rotatable frame orloop aerial G of one or more turns and of suitablearea in closed circuitwith which are included the variable tuning condenser C, primary P andinductance or oscillation transformer secondaryv S Here. again betweenthe oi'nts X and Y is the coupling condenser 8 through which there iseffected a coupling which 'again balances across the terminals of theinductance L the potential differences due to the oscillations ofundesired frequency. Inthis example of my invention, the coil D, in theanode circuit of the amplifier or detectoramplifier V, is traversed bycurrent solely or predominatingly of signal frequency, having the effectupon the inductance or secondary S to change the inductance ofthe-closed circuit including the loop G as described in connection withFig. '1, the closed .circuit including the loop G during normaloperating being de-tuned with respect to the signa frequency and beingbrought back into tune withthe signal frequency by the increase of theinductance of S when the coil D is traversed by current of signalfrequency; or by reversal of coupling between D and S as described maybe in Fig. 1, the inductance, of S dccreased. bringing the closedcircuit including loop G back into tune with the signal frequency if ithad-previously been de-tunedto lower frequency,

switches s or s The operation is improved by connecting a suitable pointof the closed circuit to, earth or cormte-r-capacity E, as by closingthe switch 8 It'is desirable also to connect one terminal of theinductance L to earth or counter-capacity E, as by closing the switch 8.Either or both of the may be employed simultaneously, may be omittedwhen the parts and connections with is suitably large. a

Referring to Fig. 3, there is disclosed a modified arrangement in whichthe circuit L C is coupled to the point X through the condenser C and anadditional condenser C which capacity of the respect to earth.

or counter-capacity tion a lVith the switch a open, the antenna path isattuned, as by variable inductance L or any equivalent means, to thesignal frequency, to facilitate tuning of the circuit U, C to the signalfrequency. The-antenna path is then "dc-tuned, as by either in creasingor decreasing the inductance L thereby either reducing or increasing thefrequency of the oscillations which will be set up by static or thelike. Then the switch 8 is closed and'the circuit S, L, C is attuned'tothe ,now natural frequency of the antenna pat and the natural period ofthe secondary S accordingly is equal to the period of the oscillationsdue to static. By suitably adjusting the condenser C and the degree ofcoupling between P and S, andwith proper sense of coupling between P andS, the electro-moti've-force at the terminals of the condensers C due tothe oscillations of undesired frequency in the circuit of the secondaryS is neutralized by E through the connecor both connections to earth Emay be fixed or yariable, the circuit L C being connected to earth theelectro-motive-force of the samefrequency' impressed H d C upon theterminals .of

ie con ensers of the radio frequency i on the circuit U, C through thecoupling capacities C C". p

The advantage as regards reduction of static effects will be to lesserdegree ob tainable if the antenna path remains tuned to the signalfrequency, in which case the circuit of the secondary S, remainingdetuned to signal frequency, will admit very little energy of signalfrequency, but rel-' degree by atively greater proportion of the energyof the oscillationsdue to static, and the electromotive-force across thecondenser 0", due to the predominant or greater energy due to staticwill be annulled, due to coupling between X and Y, and the signalfrequency will redominate in effect upon the circuit L which will beaffected tofar lesser the oscillations due to static., By recourse tothe amplifier V or more of them in advance of the detector V, the signalenergy which is of lesser amplitude when the antenna path is utilized inthe condition in which it is de-tuned with respect to *thesignalfrequency is compensated for by amplification.

- The arrangeme t of Fig. 3 operates similarly when the'disturbingeffect is that of denser C 'the point Y higher, denser C there isundamped or damped waves of other signals impressed upon the antennapath. 1

In order to maintain the point Y at su1tablyhigh potential, the circuitof the secondary S is connected to earth or countercapacity E throughthe connection a, in which is included'a fixed or variable con- Bymaintaining the potential of transferred to the circuit L C a relativelygreater proportion of the received signal energy. The arrangement ofFig. 4 is similar to that of Fig. 8, except that between the point Y andthe upper terminal of the condenser C there is included an additionalfixed or variable condenser C when the switch a is closed. I Thecondenser C in a measure combines the functions of the condensers C and(l of *Fig. 3, in that it loosens the coupling between theupper terminalof the condenser C and the upper terminal of the inductance L and inthat it also serves to maintain the potential of the point Y higher.By'this arrangement there is only one coupling capacity, namely, Cbetween the point X and the upper terminal of the inductance L Thiscircuit arrangement is employed in general as described in connectionwith Fig. 3. Here'again the antenna path and the circuit L, C areattuned to the signal frequency, whereupon the antenna is detuned, thecircuit of the secondary S attuned. 'to the now period of the antenna,and the switch .9 then closed. The operation is in general, both forartificial and natural disturbances, substantially that describedi inconnection with Fig. 3.

Referring to Fig. 5, the arrangement is in some respects similar to thatshown" in Fig. 4, particularly as regards the employment of thecondenser C". In this case, however, the grid 9 of the amplifier Visconnected'directly to the point Y, and the coupling between -X and Yis effected through a variable inductive or non-induc- Between thepoints X and as effected by the con- 'L ,,-\C to the signal frequency.

of the preceding figures, it being understood to Fig. 6, there is in theanthe tuning inducta nce L, the primary P and the primary P. Variablycoupled to the primary 1? is the secondary S in circuit with which isthe variable tuning inductance L and variable tuning capacity C 9, aconnection to earth or counter-capacity E being made through a Y isagain em- ,ployed the coupling capacity G which may be connected eitherthrough the switch 8 .or s to a point between secondary S and inductanceL or to a point between inductance L and condenser C the connectionthrough switch .8 being preferred. The grid circuit ofthe detector V isconnected across the terminals of the condenser C The potential of thepoint X is carried directly to the point X through which it isimpressed, when the switch 8 is closed, through the variable condenser Cto one terminal of the condenser C in the circuit of the secondary S.The

other terminal of the condenser C communicates through the connection a.with earth or counter-capacity E and inductance L which with thegtuningcondenser C is attuned to the signal frequency which is impressed uponthe grid 9 of the radio frequency amplifier V which may be utilizedalone or may be supplanted by several stages of 'radio frequencyamplification. In the plate circuit of tube V, or in the plate circuitof the last amplifier, when there is a series of radio frequencyamplifiers,-is the driver coil D, functioning similarly to driver coil Dof Fig. 1, when the switch 88 is thrown to the left.

The antenna path is first tuned to the signal frequency, neither switch8 nor 8 being closed, and switches s and 8 being open, to facilitatetuning of the circuit 8*,

' The switch 8 is now closed, bringing the inductance or secondary Finto parallel with the primary P the inductance of which latter ispreferably materially greater than the inductance of F. This de-tunesthe antenna with respect to the signal frequency, and, as hereinbeforedescribed, the signal energy appears as forced oscillations while theoscillations due to static are free oscillations. The coil F being oflesser inductance than the primary P and beingin parallel therewith, thegreater proportion of the energies of the oscillations representingsignal and due to static flow by the branch F to earth E, and thereappears in the circuit of the secondary S greatly reduced oscillationsrepresenting signal and due to static. There result correspondinglyfeeble electro-motive-forces of signal and undesired frequenciesacrossthe terminals of the condenser C and these are neutralized, wheneither of the switches. s or 8 is closed, by suitablyadjusting thecondenser C Under these circumstances, the grid 9 of the detector V isnot influenced by either of the signal-representing oscillations nor theoscillations due'to static, and there is no effect upon or intheinstrumentT.

Now the switch 8 is closed, whereby the potential at thepoint X equal tothe potential at the point X, is impressed across the condensers C", Cand inductance L through the connection a to earth or counter-capacityE, and the circuit L C being attuned to signal frequency, there flowsinto the driver coil D an amplified current of signal frequency whichincreases, as hereinbefore described, the impedance of the coil F,thereby causing transfer into' the circuit: of the secondary S tuned tosignal frequency, of energy of signal frequency, greatly pre dominatingover the energy of undesired frequency in the circuit of the secondary Swith the result that the grid of-the tube V is subjected to potentialvariations at signal frequency, causing the instrument T to respond tothe signal energy and to be af-. fectedionly'in slight degree by theenergy of undesired .frequency. The operation may be improved, however,by closing the switch s, whereupon the circuit S, L, C, attuned to theundesired frequency, is traversed by current of undesired frequencycausing across the terminals of the condenser C an electro-motive-forceof ,the undesired frequency which is neutralized, however, by thecoupling froin point through switch 8 and condensers C", C,v andinductance L with the result that such smaller proportion of the energyof undesired frequency previously present in the inductance L iseliminated and the current now traversing the driver coil D is purely ofsignal frequency, with the result that the effects of static are morecompletely eliminated from the instrument T.

- In the foregoing description of theoperation of Fig. 6, and in thedescription of the operation of Figs. 1 to 5 inclusive, there has beenassumed to be transmitted from the distant co-operating transmittingstation uudamped Waves modulated in accordance with sound' waves, as fortelephony, or decadent wave trains for telegraphy. However, when thedistant co-operating station is transmitting undamped waves for pur-,poses of telegraphy, the telegraphic signals may be rendered audiblein-the instrument '1 by heterodyne action, as by impressing upon thecircuit of the grid 9. oscillatory energy locally produced and of afrequency differing from the signal frequency by an amount to produceaudible beats. H repre- .tro-motive-forces across the terminals of the.t.

sents a source of high frequency oscillations, of frequency differingfrom the signal frequency, which may be impressed upon the grid circuit,upon closure of the switch 8" through oscillation transformer t. It willbe obvious also that when the. ar-- rangements of Figs. 1 to 5 inclusiveare to be utilized for telegraphy employing un damped waves, a generatorsuch as H may be coupled to the grid circuit of any of the detectortubes V.

By opening the switches a and s, or by entirely omitting thetransformer'P, S, all connections and apparatus below the point Xincluding omission of the amplifier V and by throwing the switch s tothe position indicated, and by opening switclns the'source of highfrequency sustained oscillations I is connected to the driver coil D,when it is desired to receive telegraphic signals transmitted byundamped waves.

With the switches 8 s and 8 open, the antenna path is tuned to' thesignal frequency, as is also the circuit of the secondary S Switch 8 isthen closed, where'- upon the antenna circuit is de-tuned with respectto the signal frequency, and then either. of switches a or s is closed,and the condenser C adjusted to neutralize the 'elec.

condenser C due to the oscillations of'signal frequency andundesiredfrequency, and under these circumstances there is no efiect upon theinstrument T. Then by closing the switch a with the source Ioperative,there flows through the coil D sustained oscillations of a frequencydiffering at'least from the signal frequency. By suitably adjusting thedegree of coupling between D and F, and without regard to sense ofcoupling be- 05 tween D and F, the current in the coil D develops in thecoil F an electro-motive-force which prevents flow through the coil F ofoscillations of signal frequency, in effect increasing the.impedanc eofthe coil F and m compelling a greater proportion of the signalfrequency to' be transferred from primary P to the circuit of thesecondary S thereby producing an effect upon the instru ment T by thesignal frequency and to some 5 extent by the energy of undesiredfrequency. The frequency of the oscillations from the source I beingdifferent fromthe signal frequency, the signal energy controlling theinstrument T rises and falls in amplitude at audio frequency dependentupon the differvence between'the signal frequency and the frequency ofthe oscillations from source 'I.- The amplitude of the current in Finduced- I from the coil D is preferably made such as to be equal tothe. amplitude of the signal oscillations in the coil F, with the resultthat I the beatefl'ect is amaximum because of substantial equality ofthe amplitudes of. the reactlng' currents. The oscillations of undesiredfrequency simultaneously existing in the coil F are generally of fargreater amphtude, at least at the beginning of the wave train ofundesired frequency, than the amplitude of the signal oscillations, withthe result that only a small and unimportant 'beat effect results fromthe reaction of the currents'induced. in the coil D upon the ourrents ofundesired frequ'ency in the coil F, with the result that in theinstrument T the beatQeifect due to the signal energy greatlypredominates over the beat efi'ect resulting from the oscillations dueto static, and the telegraphic signals are readily d1st1ngu1shand switch8. closedor not, no effects of static can reach the telephone T duringthe spaces between telegraphic characters, it beingassumed in thisconnection that the generator H is in operation and switch? .9 closed.

For the sake of brevity in the appended claims, the term signal isemployed generically to include signals of any character, includingtelegraphic and telephonic signals, and any other analogous efl'ect,including controls; and the term static 1s ge nerically employed toinclude static and other natural electrical effects andalso othereffects having artificial origin such as are caused or represented by"waves or ,0scilla-' tions other than those representing the desiredsignal or control.

' vated potential in said first named What I claim is: 1. The method ofreducing the efi'ect of static in reception of signals, which ,com-

prises receiving the signal oscillations in a path in which staticoscillations occur, transferring static oscillations to a second path,applying to said second path an electroinotive-force derived from apoint of eleath to reduce the effect of said'static 'osci lations,subjecting a signal circuit to an 'electromotive-force derived from apoint of elevated potential in 'said first named path,

and "translatinginto a signal thd signaloscillations of said signalcircuit.

2. The method of reducingthecffect of MStatic in reception of signals,which comprises receiving the signal oscillations in a path in WlllCllstatic oscillations occur, transi ferring static oscillations to. asecond path,

applying to said second path an electromotive-force derived from a point'ofelevated potential in said first named path to reduce the'eflect ofsaid sta'ti'c oscillations, subjecting'a signal circuit to anelectromotive-force derived from said point of elevated potential insaid first'n'amed path,.and

reduce the effect of said static oscillations, 'SllbJBCtlIlg a signalcircuit attuned. tothe frequency of the signal oscillations to anelectro-motwe-force derived from a point "of elevated potential in saidfirst named path,

and translating into a signal the signal oscillations of said signalcircuit.

4. The method of reducing the effect of static in reception of signals,which comprises receiving the signal oscillations in a path in whichstatic oscillations occur, de-tuning said path with respect to thefrequency of the signal oscillations, transferring static oscillationsto a second path at-. tuned to the frequency of said staticoscillations, applying to said second path I an electro-motive-forcederived from a point of elevated potential in said first named path toreduce the effect of said static oscillations,

' subjecting a signalcircuit attuned to the frequency of the signaloscillations to said 'point of elevated potential in said first namedpath, and translatin into a signal the signal oscillations of sai signalcircuit.

5. The method of reducing the effect of static in reception of signalsin a receiving system comprising a path in which occursignal and staticoscillations, a path receiving static oscillations from said first namedpath, and a signal circuit coupled to said second path, which comprisesimpressing on said second path and said signal circuitelectro-motive-forces froma region of elevated potentiali in said firstnamed pathto reduce the'eflect of static oscillations in said secondpath and .to efi'ect signal oscillations in said signal circuit, ,andtranslating into a signal the signal oscillations ofsaid signal circuit.

6. The method of reducing the effect of static in reception of signalsin a receiving system comprising a path .in' which. occur signal andstatic oscillations, a path receivingstatic oscillations fro'msaidfirstnamed I path, and a signal circuit coupled to said second path,which comprises de-tuning the said first named'path with respect to the,frequency of the signal oscillations, impressingupon said second ath andsaid signal circuit electro-motiveorces from a regionofelevatedpotential in said first named path to reduce the effect ofstatic oscillations in said second path and to effect signaloscillations in said signal circuit, and translating into a signal thesignal oscillations of said signal circuit. I

7. The method of reducing the effect of static in reception of signals,whichcomprises receiving the signal oscillations in a path in whichstatic oscillations occur, transferring static oscillations to a secondpath, applying to said second path an electro-motive-force derived froma point ofelevated potential in said first named path to reduce theeffect of said static oscillations, subjecting a signal circuit to anelectro-motiveforce derived from a point of elevated potential in saidfirst named path, amplifying the signal oscillations of said signalcircuit,

varying the impedance of said first named -path by said amplifiedoscillations, and

translating the signal oscillations into a signal.

8. The method of reducing the effect of static in reception of signals,which comprises receiving the signal oscillations in a path 111 whichstatic oscillations occur,

dc-tuning said path with respect to the frequency of the signaloscillations, transferring static oscillations to a second path,applying to said second path an electrosmotiveforce derived from a pointof elevated potential in said first namedpath to reduce the effect ofsaid static oscillations, influencing a signal circuit by the signaloscillations in. said first named path, amplifying the signaloscillations of said signal circuit, aryingthe, impedance of said firstnamed path by said amplified oscillations to give to said first namedpath a period corresponding substantially with the period of the signaloscillations, and translating the signal oscillations into a signal.

9. The method of reducing the effect of static in reception of signals,which comprises receiving the signal oscillations in a path in whichstatic oscillations occur, transferring oscillations from said path to acircuit,'ap flying to said circuit an electromot iveorce derived from apoint of elevated potential in said path to reduce the effect oftheoscillations in said circuit, subjecting a signal circuit to anelectro-motiveforce derived from a point of elevated po tential in saidpath, translating into a signal the oscillations of said signal circuit,applying to a third circuit an electro-mot1veforce of signal frequencyderived from a point of elevated potential. in said path,

amplifying theoscillations of signal fre quency of said third circuit,and controlling the aforesaid transfer of oscillations from said pathinto said first circuit by said amplified oscillations.

10. The method of reducing the effect of static in reception of signals,which comprises receiving the signal oscillatlons in a path in whichstati oscillations occur, transferring oscillations from said path to acircuit, applying to said circuit an electric-motive-force derived froma point of elevated potential in said path to reduce the effect of theoscillations in said circuit, subjecting a signal circuit to anelectro-motiveforce derived from a point of elevated potential in saidpath, translating into a sig nal the oscillations of said signalcircuit, applying to a third circuit anelectro-motire-force of signalfrequency derived from a 'a' point of elevated potential in said path,amplifying the oscillations of signal frequency of said third circuit,transferring from said path to a fourth circuit oscillations of staticfrequency, applying to said fourth circuit an electro-motive-force fromapoint of elevated potential in said path for reducing the effect ofthe-oscillations of static frequency of said fourth circuit upon saidthird circuit, and controlling the transfer of oscillations from saidpath to said third circuit by-said amplified oscillations.

11. The method of reducing the effect of static in reception of signals,which comprises receiving the signal oscillations in a path in whichstatic oscillations occur, transferring oscillations from said path to acircuit, applying to said circuit an electromotive-force derived from apoint of elevated tpotential in said .path to reduce the effect of theoscillations in said circuit, subjecting a signal circuit to a point ofelevated potential in said path, translating into a signal, theoscillations of said signal circuit, applying to a third circuit anelectro-motive-force of signal frequencyderived from a point of elevatedpotential in said path, amplifying 5 the oscillations of signalfrequency of said third circuit, controlling the aforesaid transfer ofoscillations from said path into said first circuit by said amplifiedoscillations, and causing locally producedoscillations to react with thesignal oscillations to produce an audible signal.

12. The method of reducing the effect of static in reception of signals,which comprises rceiving the signaloscillations in a path in whichstatic osclllations occur, 11; transferring oscillations from, said pathto a circuit, applying to said circuit an electromotive-force derivedfrom a point of elevated potential in said path to reduce the effect ofthe oscillations in said circuit, subject-- ing. a signal circuit to anelectro motiveforce derived from a point of elevated potential/in saidpath, translating into a signal the oscillations of said signal circult,applying to a third circuit an electro-mo- 1 tive-force of signalfrequency derived from a point of elevated potential in said path,amplifying the oscillations of signalfrequency of said thirdv circuit,transferring from said path to a fourth circuit oscillationsof staticirequen'cy, applying to said fourth circuit an electro-motive-force froma point of elevated potential in said path for reducing the effect ofthe oscillations of static frequency of said fourth'circuit upon saidthird circuit, controlling the transfer of oscillations from said pathto said third circuit by said amplified oscillations, and

causing locally produced oscillations-tom a e with the signaloscillations to produce a audible signal. 7

13. The method of reducing the efiect of static in reception of signals,which comall prises receiving. the signal oscillations in a path inwhich static oscillations occur, transmitting oscillationsi fromsaid'path to a circuit, applying to said circuit an electromotive-forcederived from a point of elevat-' ed potential in said path to reduce theeffect of said oscillations in said circuit, subjecting a signal circuitto. an electro-motive-force derived from a point of elevated potentialin said path, translating into a signal the oscillations of said signalcircuit, independently generating oscillations of a frequency difl'eringfrom said signal oscillations, and

controlling said transfer of oscillations 'afiected by said first namedtranslating instrument control ed by said from said path to saidfirstnamed circuit by said locally generated oscillations.

14. A receiving system comprising a path traversed by signal and staticoscillations and detuned with respect to the signal oscillations, asecond path, a coupling between said paths, a coupling .from a. .pointof elevated potential in said first named path to said second namedpath, a signal circuit coupled to said first named path independently ofsaid first named coupling, and a translating instrument controlled bysaid signal circuit. p i

15. A receiving system comprising a path traversed by signal and staticoscillations and detuned with respect to the signal oscillations, a,second path, a coupling between said paths a coupling connection betweensaid secon ath and a point of elevated po-; tential .in sald first namedpath, a capacity in said coupling connection, a signal circuitath,'-ai1d a signal circuit.

X traversed by sign I traversed by signal and static oscillations anddetuned with respect to the signal oscilf- I ean??? lations, asecondipath, a coupling between said paths, a coupling connectionbetween said second. path anda point of elevated potential in said firstnamed path, a signal circuit coupled to said first named path throughsaid coupling connection, a capacity in said-couplingconnection, and atranslating instrument controlled by said signal circuit. p

18. A receiving system comprising a path traversed by signal and staticoscillations, a second path, a circuit coupled to said paths, a signalcircuit, means coupling said circuits to each other, means coupling saidcircuits to a region of elevated potential in said'first named path, anda translating instrument controlled by said signal circuit.

b 19. A receiving system comprising a path transversed by signal andstatic oscillations, aYsecond path, .a circuit coupled to said paths,. asignal circuit, means coupling said circuits to each other, a connectioncoupling said-circuits to a point of elevated potential in saidfirst/named path, and a translating instrument controlled by saidsi'gnalcircuit. 20. A receiving system comprising a path traversed by signaland static oscillations, a-

second path, acircliit coupled to said paths, 9. signal circuit, meanscoupling said circuits to each other, means coupling said circuits to aregidn of elevated potential in said first named path, a capacity insaid coupling connection, and a translating instrument controlled bysaid signal circuit." v

21.. A receiving system comprising a path traversed by signal and staticoscillations, a

second path, a circuit coupled to said paths,

a signal circuit, means common to said circuits coupling them, meanscoupling said circuits to a region of elevated potential in said firstnamed path, and a translating instrument controlled by said signalcircuit.

22. A receiving system comprising a path traversed by signal and staticoscillations, a

second path, a circuit coupled to said paths,

a signal circuit, means common to said circuits coupling them, aconnectlon coupling said circuits to a point of elevated potential insaid first named path, and a translating instrument controlled by saidsignal circuit.

23. A receiving system comprising a path traversed by signal and staticoscillations, a

second path, a circuit coupled to said paths, a signal circu1t,'meanscommon to said 011E cuits coupling them, means coupling said circuitstoa region of elevated potential in said first named path, a capacity insaid coupling connection, and a translating instru ment controlled bysaidsignaling circuit.

24:. A receiving system comprising a path traversed by signal and staticoscillations, a second path, a coupling between. saidpaths, a couplingfrom a point of elevated potential in said first named path to saidsecond named path, a signal circuit coupled to said first named pathindependently of said first .named coupling, means controlled by saidsignal circuit for amplifying the signal oscillations, means whereby theamplified oscillations affect said first named path, and a translatinginstrument controlled by said signal circuit. I

25. A receiving system comprising a path traversed by signal and staticoscillations, a second path, .a coupling between said paths, a couplingfrom a point of elevated potential in said first named path to saidsecond named path, a signal circuit coupled to said first named pathindependently of said first named coupling, inductances in parallel witheach otherin said first named path, means controlled by sa-idsignalcircuitfor amplifying the signal oscillations, a Winding inductivelyrelated to one of said inductances and traversed by the amplifiedoscillations, and a signal-translating instrument controlled'by saidsignal circuit.

26. A receiving system comprising a path traversed by signal and staticoscillations, at second path, a coupling between said paths,

a coupling from a point of elevated potential in said first named pathto said second named path, a signal circuit coupled to said first namedpath independently of said first.

named coupling, inductances in parallel with each other in said firstnamed path, one of said inductances having small induc-v tance comparedwith another of said inductances, means controlled by said signalcircuit for amplifying the signal oscillations, a

winding inductively related to said one of said inductances of smallvalue and traversed by the amplified oscillations, and asignal-translating instrument controlled by said signal circuit.

27. A receiving system comprising a path traversed by signal and staticoscillations,

inductances in parallel with each other in said path, a signal circuitassociated with said first named path, means controlled. by

said signal circuit for amplifying the signal oscillations, means'forvarying'the effective impedance of said inductances by the amplifiedoscillations, and a translating instrument controlled by said signalcircuit.

28. A receiving system comprising a path traversed by signal and staticoscillations,

- v a circuit, a coupling between said path and circuit, 'a couplingfrom a point of elevated potential in said path to said circuit forreducing the effect of the oscillations in said independently of saidfirst named coupling,

circuit, a signal circuitcoupled to said path a translating instrumentcontrolled by said signal circuit, a third circuit tuned to the signalfrequency, a coupling between said third circuit and saidpath'independent of said first named coupling, means for amplifying theoscillations of signal frequency of said third,circuit, and meanscontrolled by theamplified oscillations for controlling thea translatinginstrument controlled by said signal circuit, a third circuit tuned tothe signal frequency, a coupling between said third circuit and saidpath independent of said first named coupling, means for-amplifying theoscillations of signal frequency of said third circuit, means controlledby the amplified oscillations for controlling the transfer ofoscillations from said path to said first named circuit, a fourthcircuit tuned to the static oscillations, means coupling said fourthcircuit to said path, and

a coupling from a point of elevated potential in said path .to saidfourth circuit for re ducing the effect of the oscillations therein uponsaid third circuit.

30. A receiving system comprisiug a path traversed by signal and staticoscillations, a circuit, a coupling between said path and circuit, acoupling from a point of elevated potential in said'path to said circuitfor reducing the effect of the oscillations in said circuit, a' signalcircuit coupledto said path independently of said first named coupling,

a translating instrument controlled by said signal circuit, a thirdcircuit tuned to the signal frequency, a coupling between said thirdcircuit and said path independent of said first named coupling, meansfor ampli fying the oscillations of signal frequency of said thirdcircuit, means controlled by the amplified oscillations for controllingthe transfer of oscillations from said path to said first named circuit,a local source of oscillations, and means for causing said oscillationsto react with the oscillations of signal frequency to produce audiblebeats in said translating instrument.

31. A receiving system comprising a path traversed by signal and staticoscillations, a circuit, a coupling between said path and circuit, acoupling from a point of elevated potential in said path to said circuitfor reducing the effect of the oscillations in said circuit, a signalcircuit coupled to said path independently of said first named coupling.a translating instrument controlled by said signal circuit, a thirdcircuit tuned to the signal frequency, a coupling between sa d thirdcircuit and said path independentof said first named coupling, means forampli- "are transfer of oscillations from said path tonal frequency tothe signal oscillations in the efiect of the oscillations therein uponsaid third circuit, a local source of oscillations, and means forcausing said oscillations to react Withthe oscillations of signalfrequency to produce 'audible'beats in' said translating instrument. f

32. A receiving system comprising a path traversed by signal and staticoscillations, a circuit, a coupling between said path and circuit, asignal circuit, a translating instrument controlled by said signalcircuit, a coupling from a point of elevated potential in said path tosaid'first named circuit for reducing the efiect of the oscillationsupon. said signal circuit, a local source of oscillations of afrequencydifl'erent from the frequency of the signal oscillations, andmeans controlled by the oscillations from said local source controllingthe transfer of oscillations from said path to said first named circuitthrough said first named-coupling.

' 33. The method of reducing the veffect of' static in reception ofsignals, which comprises'receivin'g the signal oscillations in .a

, path detuned to the signal frequency and in which occur, staticoscillations of frequencydiflerent from the signal frequency,

' subjecting a second path tuned to the .signal frequency to the signaloscillations in said first named path, subjecting a third path tuned tothe static oscillations to the static oscillations in said first namedpath, and reducing the effect of static oscillations upon said secondnamed path by static oscillations in said third named ath.

' 34.- The method of reducing the. effect of static in reception ofsignals, which comprises receiving the signal oscillations in i a pathdetuned to the signal, frequency and 'in which occur static oscillationsof frequency different from the signal frequency,

subjecting a second path tuned to the s1gstatic oscillations in saidfirst named path,

3 said first named subjecting a -seeond path tuned to reducing theeffect of static oscillations Yupon said second named path by staticoscillations in said third named path, and

'utilizinglocal energy in the form of oscillations for changing thenatural period of ath.

35. The metho of reducing the effect of static in reception' of signals,which comprises receiving the. signal oscillations in a said first namedpath, subjecting a third path tuned to the static oscillations to thestatic oscillations vin said first named path, reducing the efie'ct ofstatic oscillations upon said second named'path by static oscillationsin said third named path, and utiliz- 1 quency different from the signalfrequency,

subjecting a second pathtuned to. the signal frequency to the signaloscillations in said first named path, subjecting a third path tuned tothe static oscillations to the static oscillations-in said first namedpath, reducing the effect of static oscillations up onsaid second namedpath by static oscillations in said third named path, amplifying signaloscillations, and utilizing the amplified oscillations for changing thenatural period of said first named path in a sense to approach'theperiod of the signal oscillations.

3 7. The method of reducing the effect of static in reception ofsignals, which comprises receiving the signal oscillations in a pathv.det-uned to the signal frequency and in which static oscillationsoccur, subjecting a second path to an electro-motive-force derived froma point of elevated potential in said first named path for effectingoscillations of. signal frequency in said second path, transferringstatic oscillations from said first named pathto a third path, andapplying to said thirdpath' an electro-motive-force derived from a pointof elevated potential in said first named path to reduce the efiect ofsaid static oscillations upon said second named path.

38. The method of reducing the efi'ect of static in reception ofsignals,which comprises receiving the signal oscillations in a a path detuned tothe signal frequency and in which static oscillationsoccur, subjectinga. second pathto an electro-motive-force derived from a point ofelevated potential path detuned to thesignal frequency and v in whichoccur static oscillations of frequency difiement from the signalfruency,

in said first named path for effecting oscillations of signal frequencyin said second path, transferring static oscillations from saidfirstnamed pathto a'third path, ap plying to said third path anelectro-motive-- force derived from a point of elevated potential insaidfirst named path to reduce the effect of said" static oscillations uponsaid second namedpath, and utilizing local 'energyin the form ofoscillations for changing the natural period of said first named path.

39. The method of-reducing the effect of static in reception of signals,which comprises receiving the signal oscillations in a path detuned tothe signal frequency and in which static oscillations occur, subjectinga second path to an ele'ctro-motive-force derived from .a point ofelevated potential in said first named path for effecting oscillationsof signal frequency in said second path, transferring staticoscillations from said first named path to a third path, applying tosaid third path an elect-ro-motiveforce derived from a point of elevatedpotential in said first named path to reduce the effect of said staticoscillations upon said second named path, amplifying signal.oscillations, and utilizing the amplified oscillations for changing thenatural period of said first named path in a sense to approach theperiod of the signal oscillations.

40. In the reception of radio signals, the method which comprisesreceiving the signal energy in a path detuned with respect thereto, andchanging the natural period of said path by the effect of oscillationsproduced by local energy.

41. In the reception of radio signals, the method which comprisesreceiving the signal energy in a path detuned with respect thereto, andchanging the natural period of said path in a sense to approach theperiod of the signal waves by the effect of oscillations produced bylocal energy.

42. In the reception of radio signals, the method which comprisesreceiving the signal energy in a path detuned with respect thereto,amplifying the signal oscillations, and utilizing the amplifiedoscillations for changing the natural period of said path.

43. In the reception of radio signals. the method which comprisesreceiving the signal energy in a path detuned with respect thereto,amplifying the signal oscillations,

and utilizing the amplified oscillations for changing the natural periodof said path in a sense to approach the period of the signalrepresentingoscillations.

44. In the reception of radio signals, the

vmethod which comprises receiving the signal energy in a path detunedwith respect thereto, influencing a signal-translating circuit inopposite senses by the oscillations in said detuned path, whereby theefiect upon said signal-translating circuit is substantially nil, andincreasing the absorption of signal energy from said path by saidsignaltranslating circuit by influencing said path by oscillationsproduced by local energy .to substantially tune said path to thefrequency of the signal oscillations.

45. In the reception of radio signals, the method which comprisesreceiving the signal energy in a path detuned with respect thereto,influencing a signal-translating circuit in opposite senses by theoscillations in said detuned patln'wliereby the effect upon saidsignal-translating circuit is substantially nil, and increasing theabsorption of signal energy fromsaid path by said signal-translatingcircuit by influencing said path by amplified received signaloscillations to substantially tune-said path to the frequency of thesignal oscillations.

46. A receiving system comprising a path traversed by signal and staticosclllations, a path for signal oscillations, a third path detuned withrespect to the signal oscillations, and means including a plurality ofcouplings for coupling said third path to said first named path inopposite senses for reducing the effect of static oscillations upon saidpath for signal oscillations. l

47. A receiving system comprising apath detuned with respect to thesignal oscillations and traversed by-s ignal and static oscillations. apath for signal oscillations, a third. path having the same naturalperiod as said first named path, and means for coupling said third pathto said first named path in opposite senses for reducing the effect ofstatic oscillations upon said path for signal oscillations.

48. A receiving system comprising a path detuned with respect to thesignal oscillations and traversed by signal and static oscillations, apath for signal oscillations, a third path having the same naturalperiod as said first named path, means for coupling said third path tosaid first named path in opposite senses for reducing-the effect ofstatic oscillations upon said path for signal oscillations. and meansfor influencing said first named path by oscillations Whose energy is atleast in part derived from a local source of energy for changing thenatural period of said first named path.

49. A receiving system comprising a path detuned with respect to thesignal oscillations and traversed by signal. and static oscillations, apath for signal oscillations, a third path having the same natural,period as said first named path, means for coupling said third path tosaid first named path in opposite senses for reducing the effect ofstatic oscillations upon said path for signal oscillations. means foramplifying signalrepresenting oscillations. and means through which saidamplified oscillations influence said first named path to change itsnatural period in a sense approaching the period of thesignal-representing oscillations.

50. A receiving system comprising a path detuned with respect to thesignal oscillations and traversed by signal and static oscilla'tions. apath for oscillations of signal frequency, means for subjecting saidpath to an eIectro-motive-force derived from a point of elevatedpotential insaid first named path, a third path, means coupling saidthird path to said first named path, and means for applying to" saidthird" path an electro-motiveforce derived from a point of elevatedpoten tial in said first named path for preventing substantial efl'ectupon said second named path of static oscillations. 51. A receivingsystem comprising a path detuned'with res ct to the signal oscillationsand traverse by signal and static oscillations, a path for oscillationsof signal frequency, meansfor subjecting said path to anelectro-motive-force derived from a point of elevated potential in saidfirst named path,

a third path, means coupling said third'path to said first named path,means fog? applying to said third path an'electro-motive-force derivedfrom a point ofelevated potential in said first named-path forpreventing substantial efl'ect upon said second named path of staticoscillations, means for amplifying oscillationsof signal frequency, andmeans through which said amplified oscillations influence said firstnamed path to change its natural period in a sense approaching theperiod of the signal-representing oscillations.

52. A receiving system comprising a path detunedwith respect to thesignal oscillations and traversed by signal and static 0S7 cillations,and means for changing the natural period of said path comprising meansfor influencing said path by local oscillations. I v

53. A receiving system comprising a path detuned with respect to thesignal oscilla-' tions and traversedby signal and static 0sci-llations,means for amplifying oscillations of signal vfrequency, and meansthrough which the amplified oscillations influence said path to changeits natural period in a sense approaching the "period of thesignalrepresenting oscillations.

' 54. A receiving system comprising a path including'inductances ,inparallel with each other and detuned with respect to the signaloscillations and traversed bv signal and r static oscillations: andmeans for influencing one ,of said .inductances byloca-l oscillationstochange the natural period of said path.

- 55 A receiving system comprising a path 7 including inductaiices inparallel with each other and detuned with respect to the signaloscillations and traversed by signal and static oscillations, means foramplifying oscillations of-signal frequency, and means for influencingone of said inductances by the amplified oscillations for changing thenating t e period of the signal oscillations.

ural eriodlof said path in a sense approach- 56. A receiving systemcomprising a path detuned with respect to the signaljoscillationsand'tra-versed by signal and static oscillations, a'signa l-translatingcircuit, means for influencing said signal-translating [circuit inopposite senses by theoscillationsin said detuned path to render theirinfluence upon said: circuit substantially nil, and

,means for increasing theabs'orption of the energy of signaloscillations by said signaltranslating circuit from said path comprisingmeans for influencing said path by local oscillations to changeitsnatural' period in a sense approachingthe period of the signaloscillations.

57 A receiving system comprising apath detuned with respect to thesignal oscillations and traversed by signal and static 1 oscillations, asignaltranslating circuit, means for influencing. saidsignal-translating circuit in opposite senses by'the oscillations insaid detuned path to rendertheir influence upon said circuitsubstantially nil.

and means for increasing the absorption of translating circuit from saidpath compris-- inga circuit for absorbing oscillations of signalfrequency from said path, a third circuit, means for coupling saidthirdcircuit in opposite senses to said path for reduc; ing the effectof static oscillations upon said second named-circuit, means foramplifying energy of signal oscillations by said signalthe signaloscillations absorbed in said second named circuit, and means forinfluencing said path by' the amplified oscillations for changing thenatural period of said path in a. sense approaching the period of thesignal oscillations.

59. The method of reducing the eflect of static in reception of signals,which com-' prises receiving the signal oscillations in a path detunedto the si al frequency and in which occur static-oscillations offrequency difi'erent from the frequency of the signal oscillations,subjecting a second path in oposite senses to the static oscillations insaid rst named path for producing in said second path a point ofsubstantially zero potential with respect to static oscillations, and

transferr" signal oscillations from said first name path to a third paththrough said point of substantiall zero potential.

60. The method of re ucing the efiect of static in reception of signals,which comprises receiving the signal oscillatioiis'in a path detuned tothe signal fmqiiency and in which occur statib. oscillations offrequency difierent from the frequency of the signal oscillations,subjecting a second path tuned to the static oscillations in oppositesenses to the static oscillations in said first named path for producingin said second path a point of substantially zero respect to the staticoscillations, transferrin signal oscillations from said first named patto a third ath tuned to thesignal-oscillatio ns throug said oint ofsubstantially zero potential, and uti lzing local energy in the form ofoscillations for changing the natural period of saidfirst named path.

-61. The method of reducing the effect of static in reception ofsignals, .which com: prises receiving the signal oscillations in a Apath detunedto the signal frequency and in which occur staticoscillations of frequency different from the frequency of the signaloscillations, subjecting a second path tuned. to the static oscillationsin opposite senses and having a natural period which is shorter otentialwith than the period of the signal oscillations, and means forincreasing the natural eriod of said ath comprisin means for in uencing.said path by oscil ations whose energy isi'at' least in substantialproportion represented by local-energy.-

63. A receiving system comprising a path traversed by signal and staticoscillations and having a natural period which is shorter than theperiod of the signal oscillations,

means for amplifying received oscillations *of signal frequency, andmeans through which theamplified oscillations influence said path toincrease its natural period.

64. A receiving system comprising a path including inductances inparallel'with eachi.' other and traversed by signal and staticoscillations and havin a natural period shorter than the perio of thesignal oscillations, and means for influencing one of said inductancesby local oscillations to increase the natural period of said path.

65. A receiving system comprising a path including inductances inparallel w1th each other and traversed by signal and staticoscillations' and having a; natural period shorter than the period ofthe signal oscillations, means for amplifying received oscillations ofsignal frequenc and means for influencing one of said uctances by the7amplified oscillations for increasing the'nat-' u'ral period of saidpath. In testimony whereof I have hereunto affixed my signature this10th day of July,

- DAVID G. McCAA;

